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WO1990015024A1 - Enlevement de contaminants - Google Patents

Enlevement de contaminants Download PDF

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Publication number
WO1990015024A1
WO1990015024A1 PCT/AU1990/000250 AU9000250W WO9015024A1 WO 1990015024 A1 WO1990015024 A1 WO 1990015024A1 AU 9000250 W AU9000250 W AU 9000250W WO 9015024 A1 WO9015024 A1 WO 9015024A1
Authority
WO
WIPO (PCT)
Prior art keywords
liquor
foam
tank
contaminants
recovering
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/AU1990/000250
Other languages
English (en)
Inventor
David Edward Mainwaring
Ian Henry Harding
Peter Sanciolo
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Orica Australia Pty Ltd
Original Assignee
ICI Australia Operations Pty Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by ICI Australia Operations Pty Ltd filed Critical ICI Australia Operations Pty Ltd
Publication of WO1990015024A1 publication Critical patent/WO1990015024A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/24—Treatment of water, waste water, or sewage by flotation

Definitions

  • This invention relates to the removal or recovery of contaminants such as metals or organic chemicals from solution or suspension.
  • Metals particularly heavy metals, are one of the insidious pollutants of our environment. They are not biodegradable and may exist in a number of forms associated with living organisms, water, sediments and suspended matter. The heavy metals accumulate in sediments and are subsequently taken up by organisms. With the process of bio-accumulation through the food chain many edible species of aquatic life are affected to the extent that their consumption may be hazardous.
  • Sedimentation is a slow process requiring large settling volumes.
  • the conventional process is also subject to number of interferences which can effect the rate of settling - particularly if the system uses NaOH for neutralization.
  • Even well operated clarifiers can have 5 to 50 ppm of suspended solids in the overflow.
  • Contaminants such as oils and substances which produce gases, are the most common source of problems since they interfere with the sedimentation process by increasing the buoyancy of the particles.
  • the flocculants used to speed up the sedimentation process in conventional technology are almost exclusively organic polyelectrolytes . These are expensive and require a certain degree of mixing before clarification is attempted. Depending on the size of the clarifier used, a separate mixing zone may be required in the process. The polyelectrolytes also add to the volume of sludge generated.
  • Adsorbing colloid flotation has a number of attractive features (i) low energy requirements (ii) high removal efficiency (ifi) reasonable capital requirements and (iv) comparatively low maintenance and operating costs, thereby potentially providing a low cost method of heavy metals recovery from industrial wastewaters.
  • the process generally involves the production of a hydroxide precipitate of the metal ions via pH adjustment by adsorption and/or co-precipitation with a floe generating material such as Fe(0H) 3 or AKOH),, rendering the floe hydrophobic by adsorption of a surfactant and its subsequent removal by flotation with air bubbles.
  • the present invention provides a method of recovering contaminants from suspension or solution in a liquor which comprises the steps of forming a foam of the liquor, displacing said foam onto a drainage device to dry said foam, and separate the liquor said contaminants being retained in the dried foam and the drained liquor being reduced in contaminant content.
  • the present invention produces a foam which carries the majority of the liquor, with it over the top of the foaming tank onto a drainage device.
  • the foam flows over the drainage device and dries, that is it is dewatered by drainage resulting in separation of the liquor from the foam.
  • the dried foam may then be collected and disposed of.
  • the liquor reduced in contaminant levels is collected from the drainage device.
  • a method of recovering waste water contaminants from a liquor such as waste water comprising the following steps: feeding the liquor into a tank; forming a foam by passing gas through the liquor such that greater than 50% by volume of the liquor fed into the tank is displaced by overflow from the tank in the form of a foam; draining the foam; and collecting the liquor drained from the foam said liquor having reduced contaminant levels.
  • This invention generally achieves much faster throughput and lower resistance times in the foaming tank with a consequent saving in plant size.
  • the foaming step in the process of the invention is generally carried out on the liquor in the presence of a collecting colloid and surfactant.
  • the degree of removal of the contaminant is partly predicated on the choice of collecting (or adsorbing) colloid.
  • the adsorbing colloid is a metal hydroxide or metal sulphate of low water solubility and preferred adsorbing colloids are generally selected from hydroxides and sulfates of iron and aluminium and mixtures thereof.
  • Preferred adsorbing colloids are Fe(OH)- ,Fe(0H) 2 and A1(0H) 3 particularly in the case of heavy metal contaminants.
  • the level of adsorbing colloid is typically in the range of from 1 to 1000 ppm and preferably in the range of from 5 to 500 ppm.
  • the adsorbing colloid comprises a mixture of Al(OH), and one or both of Fe(0H> 3 and Fe(0H) 2 which is preferably in a molar ratio in the range of from 5:1 to 1:5 and most preferably in the range of Al to Fe of from 1:1 to 1:4.
  • the absorbing colloid may be formed in situ under the appropriate conditions.
  • the surfactants used are selected to provide a persistent, rigid, elastic foam. It is desirable that the foam persists for a sufficient period to allow efficient draining of the liquor from the foam and good retention of contaminants. Typically the foam will persist for at least 30 minutes without collapsing and preferably at least 2 hours at ambient temperature and pressure. Most preferably the foam persists until it is dry.
  • a foam having rigidity means it is unlikely to collapse while rising in the foaming tank or moving on the drainage device. Elasticity of the foam allows it to move out of the tank and over the drainage device.
  • the surfactant comprises a mixture of at least one metal salts of a fatty acid or C g to C.g aliphatic alcohol and at least one metal salt of a fatty alkyl sulfate.
  • the level of surfactant is preferably in the range of from 5 to 5000 ppm and preferably from 10 to 500 ppm of liquor.
  • the molar ratio of fatty acid salt to fatty alkyl sulphate is in the range of from 1:1 to 1:4.
  • a particularly preferred surfactant component comprises a lauryl sulphate salt such as sodium lauryl sulfate in combination with an acid salt when the acid is selected from oleic, lauric and hexanoic acid.
  • a lauryl sulphate salt such as sodium lauryl sulfate in combination with an acid salt when the acid is selected from oleic, lauric and hexanoic acid.
  • the weight ratio of one part sodium laurate to two parts sodium lauryl sulfate and preferably 40 ppm of sodium laurate and 80 ppm of sodium lauryl sulfate is used.
  • Another mixture of interest is sodium oleate and sodium lauryl sulfate.
  • gas is used in the formation of foam any suitable gas may be used. Air is preferred on economic grounds however nitrogen may be of particular use where it is desired to minimise oxidation of metal.
  • Shorter residence times are a result of the increase in the volume of liquor and entraining air relative to each other and relative to the volume of the foaming tank.
  • By increasing the volume flow rate of the liquor and of the foaming gas relative to the volume of the tank residence times are reduced.
  • Volume ratios of air to water in the range of from 5:1 (preferably 5:2) to 5:3 are generally convenient.
  • the optimum throughput of liquor may be determined without undue experimentation having regard to the method described herein.
  • the throughput in the foaming tank may conveniently be measured in terms of hydraulic loading which may be, for
  • the required gas flow rate for a given system may be determined having regard to the need for efficient foaming and may depend on various factors such as the surfactant choice. We have typically used gas flow rates of at least
  • 25Nm /m h for example in the range of from 30 to 70 Nm /m h.
  • the foam will be allowed to drain so that at least 95% by volume of the liquor is recovered from the foam.
  • the nature of the drainage device is not narrowly critical but will be dictated by its function of providing drainage of liquor while allowing the foam to remain intact.
  • the drainage device may comprise racks or trays which allow the foam to progressively move under force of gravity and/or by the urging of newly created foam.
  • trays or racks may be stacked such that foam is progressively transferred to a lower level as it dries.
  • foam it fs convenient to allow the foam to dry under ambient temperature and pressure, however variation of temperature, pressure or gas currents may be used to quicken drying if desired.
  • metals including aluminium and heavy metals being metals of atomic number of at least 21, such as Titanium Chromium, Manganese, Cobalt, Nickel, Copper, Zinc, Yttrium Zirconium, Molybdenum, Antimony, Tungsten Palladium, Silver, Cadmium, Tin, Mercury, Lead and Uranium
  • organic chemicals such as synthetic and natural oils.
  • the process of the invention has been found to be particularly suited to removal of metals such as Aluminium, Chromium, Nickel, Copper, Zinc, Antimony, Lead and Mercury. Such metals may be in the form of the elemental metal or its compounds or ions.
  • the organic chemical most suited to removal by the process of the invention generally have a low water solubility for example, a water solubility of less than lOmg per litre.
  • the method of the invention generally provides at least 95% by weight retention of heavy metals in the foam.
  • the level of contaminants in the liquor prior to treatment may be for example, in the range of from 0.1 parts per billion to 5000 parts per million.
  • the process of the invention may also be used in combination with conventional methods such as precipitation.
  • the theory of the foam collection is as follows. It is well known that for a material to be removed by flotation it must form a stable three phase contact at the interfacial region created by the separate solid/liquid S/L, solid/gas S/G and liquid/gas L/G interfaces. The three corresponding interfacial free energies are related to the contact angle, measured through the liquid phase, by Young's equation.
  • a surface active molecule is adsorbed onto the surface to given a sufficient value to c ⁇
  • Bleier (1977) has shown that the property that determines ultimately whether a bubble and a particle heterocoalesce is this relative hydrophobicity of the solid's surface.
  • FIG. 1 is a schematic plan of a treatment plant adapted to treat waste water in accordance with this invention.
  • wastewater to be treated is introduced to the holding or pretreatement tank 1 where stirrer 2 mixes the waste water to provide an even consistency.
  • Wastewater is continously fed into the foaming tank 7 by pump 3 and surfactant is continuously pumped by pump 5 into the wastewater prior to the wastewater entering the foaming tank.
  • Foam is continuously produced from the wastewater in the tank 7 by air introduced by pump 6 at or adjacent the bottom of the tank 7 and overflows from the tank 7 via overflow conduit 8 onto stacked drainage trays 9.
  • Foam drains as it passes over the trays under the action of gravity and the urging of newly created foam and dried foam is collected in bin 10.
  • Drained liquor is recovered via conduit 11 for further treatment or safe disposal.
  • a laboratory scale plant of the design described above with reference to Figure 1 was used to separate heavy metals from effluent from an electroplating installation.
  • the samples were all chromium stream samples which had already been treated with metabisulfite at pH3 to reduce Cr VI to Cr III.
  • the level of heavy metals in these samples was in the following ranges:
  • a foam was generated by passing air through a porous glass air diffuser at the bottom of the flotation cell.
  • the foam was collected in wide, shallow containers which allow dewatering and concentration of the foam product to 5% solids.
  • the treated effluent was sampled at regular intervals during each run and analysed for Cr, Ni and Zn by atomic absorption spectroscopy.
  • the process is able to meet the 10 ppm limit for the disposal of these metals to sewer at very high feed flow rates. (Residence times of 0.7 minutes in flotation cell).
  • the average small electroplating firm produces approximately 12,000 litres of wastewater per day.
  • the semi-bench scale rig used above operated at 190 1/hr. Hence, in a 12 hour day this rig can treat 2,160 litres of water.
  • the foam exiting the floation column contains substantial quantities of water. Before this is disposed of, it must first be dewatered and concentrated.
  • Foam drainage rate experiments revealed that wide and shallow collection vessels (ie of high surface are to volume ratio) were the most effective in dewatering and concentrating the foam product by facilitating the drainage process. It was found that if the fresh wet foam was allowed to enter one end of a wide and shallow collection vessel, by the time the foam reached the other side of the collection vessels considerable dewatering and concentration had taken place.
  • Alkali Both the conventional process and this invention being developed depend on the precipitation of the heavy metal with alkali.
  • the pH at which the maximum removal of heavy metals is achieved depends on the solubilities of the heavy metal hydroxides and to some extent on which heavy metals are present. With the conventional process, although the pH for the maximum removal of the heavy metals may have been achieved, more alkali is added to raise the pH to the optimum pH for the flocculation stage (pH 9-10).
  • the flotation process may operate at pH 7.5-8.0 and hence does not need this additional use of alkali.
  • Surfactant or flocculant The polymer flocculants used in conventional technology are used at a ' lower level than the surfactants in the flotation process (approximately 5 ppm for flocculants compared with approxmately 60 ppm for the surfactants). - This added expense associated with the use of surfactants would, however, be partially offset by the fact that the surfactants used are less expensive than polymer flocculants.
  • Wastewater containing 620mg/l fibremakers spinning oil was foamed in accordance with the procedure of Example 1 using a batch process and the surfactant was present as 40 ppm sodium laurate and 80 ppm sodium lauryl sulfate.
  • the liquor drained from the foam contained 60 mg/1 spinning oil.
  • This Example demonstrates the use of the invention in removal of mercury from the industrial waste water.
  • surfactant to provide 100 ppm sodium laurate and 200 ppm sodium lauryl sulphate and aluminium nitrate and ferrous sulphate were welded to provide 100 ppm A1111 and 100 ppm Fell.
  • the pH was adjusted to 8.5 by addition of NaOH.
  • the mixture was farmed according to the process of Example 1 using the apparatus of Fig. 1 and the liquor drained from the foam was found to comprise 11 parts per billion mercury.
  • the waste water mixture was prepared and treated as for Example 3 with the exception that the pH was altered by variation of the amount of NaOH added.
  • Example 3 The process of Example 3 was repeated with varying concentration of A1III and Fell. The efficiency of removal of mercury at the varying adsorbing colloid concentrations is tabulated below.
  • Example 3 The procedure of Example 3 was repeated using a waste water sample having a mercury concentration of 56 parts per billion and the removal of Hg using various adsorbing colloid concentrations is shown in the table below.

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  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Physical Water Treatments (AREA)
  • Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)

Abstract

Un procédé de récupération de contaminants de la suspension ou de la solution dans un liquide comprend la formation d'une mousse du liquide et le déplacement de ladite mousse vers une installation de drainage servant à assécher ladite mousse et à séparer le liquide, lesdits contaminants étant retenus dans la mousse sèche et le liquide évacué ayant un contenu en contaminants réduit.
PCT/AU1990/000250 1989-06-08 1990-06-07 Enlevement de contaminants Ceased WO1990015024A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
AUPJ461089 1989-06-08
AUPJ4610 1989-06-08
AU57240/90A AU638717B2 (en) 1989-06-08 1990-06-07 Removal of contaminants

Publications (1)

Publication Number Publication Date
WO1990015024A1 true WO1990015024A1 (fr) 1990-12-13

Family

ID=25631576

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/AU1990/000250 Ceased WO1990015024A1 (fr) 1989-06-08 1990-06-07 Enlevement de contaminants

Country Status (3)

Country Link
EP (1) EP0483157A4 (fr)
AU (1) AU638717B2 (fr)
WO (1) WO1990015024A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5535893A (en) * 1989-10-19 1996-07-16 University Of Newcastle Research Associates Ltd. Method and apparatus for separation by flotation in a centrifugal field
RU2160713C2 (ru) * 1999-02-09 2000-12-20 Горный институт Кольского научного центра РАН Способ очистки сточных вод

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2268726A (en) * 1938-10-14 1942-01-06 Link Belt Co Floc concentration tank
US4268379A (en) * 1977-12-23 1981-05-19 American Cyanamid Company Selective flocculation for increased coal recovery by froth flotation
US4790944A (en) * 1986-03-27 1988-12-13 Cjb Developments Ltd. Process and apparatus for the separation of foreign matter from a liquid by flotation

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4198294A (en) * 1975-06-16 1980-04-15 The Redux Corporation, Inc. Water purification system
US4203837A (en) * 1976-01-16 1980-05-20 Hoge John H Process for removal of discrete particulates and solutes from liquids by foam flotation
US4738784A (en) * 1986-07-03 1988-04-19 Kazutoyo Sugihara Flotation device
US4743379A (en) * 1986-07-03 1988-05-10 Kazutoyo Sugihara Flotation device

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2268726A (en) * 1938-10-14 1942-01-06 Link Belt Co Floc concentration tank
US4268379A (en) * 1977-12-23 1981-05-19 American Cyanamid Company Selective flocculation for increased coal recovery by froth flotation
US4790944A (en) * 1986-03-27 1988-12-13 Cjb Developments Ltd. Process and apparatus for the separation of foreign matter from a liquid by flotation

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP0483157A4 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5535893A (en) * 1989-10-19 1996-07-16 University Of Newcastle Research Associates Ltd. Method and apparatus for separation by flotation in a centrifugal field
RU2160713C2 (ru) * 1999-02-09 2000-12-20 Горный институт Кольского научного центра РАН Способ очистки сточных вод

Also Published As

Publication number Publication date
AU5724090A (en) 1991-01-07
EP0483157A1 (fr) 1992-05-06
EP0483157A4 (en) 1992-08-19
AU638717B2 (en) 1993-07-08

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